A Regional Analysis Of Factors Affecting Adult Female Elk Survival

The Western Elk Research Collaborative has pooled elk (Cervus elaphus) telemetry data from seven states, one Canadian province, and Yellowstone National Park. We haven collected data from 3550 individual elk across 51 populations. The vast spatial scale of this analysis affords us an unprecedented opportunity to understand how natural ecological conditions and human changes to the environment influence survival of this critical segment of the population. We use proportional hazards models and information-theoretic approaches to assess how predator diversity, harvest by humans, habitat conditions, land use, climatic factors, and interactions between these factors affect adult female survival across the region. Most of our variables are uniform within a given population, but we also assess the effects of "age" at the individual level. Some variables such as land tenure, road density, and forest cover are considered temporally static for the purposes of this study, whereas others such as precipitation, climate, and density dependence could vary over time within each population. The survival estimates we generate will ultimately help inform decision-support tools that managers could use at statewide and regional scales to explore how harvestable numbers of elk are influenced by management of habitat and predation in the context of climatic and habitat changes

Effects of seed dispersal by gibbons, sambar, and muntjac on Choerospondias axillaris demography, and the disruption of this mutualism by wildlife poaching

Rampant illegal hunting threatens wildlife populations inside many tropical protected areas, compromising their long-term effectiveness. A critical question concerns whether such harvest has indirect effects on non-hunted organisms that interact with the game species. For example many tree species are demographically reliant on seed dispersal by vertebrates that are threatened by hunting; the anthropogenic disruption of this animal-plant mutualism can severely alter the composition of tropical forests. Here I show that illegal poaching has reduced or extirpated several mammal species from national parks in northern Thailand. This, in turn, has negatively affected the demography of the canopy tree Choerospondias axillaris, which is dependent on the dispersal of its seeds to light gaps by gibbons (Hylobates lar), sambar deer (Cervus elaphus), and muntjac deer (Muntiacus muntjak). In parks where these mammals are heavily hunted, far fewer seeds are dispersed to light gaps and seedling abundance is significantly reduced. These results suggest that anthropogenic impacts such as overharvest can indirectly ramify through communities. I also assessed the functional equivalence of the three seed-dispersing mammals in terms of their demographic impact on C. axillaris. Sambar and muntjac dispersed far more seeds than gibbons. Sambar deposited many seeds under female tree canopies; muntjac were the only disperser to deposit seeds in the most open habitats, which are beneficial for C. axillaris seed germination, seedling survival and growth. Using stage-based population models, I assessed how disperser-specific seed dispersal, variation in the frequency of canopy gap formation, and the interactive effects of these factors on plant demography influence the long-term population growth of C. axillaris. Large differences in dispersal quantity and small differences in dispersal quality, when placed in a biologically complex population-level context, resulted in only marginal variation in the impacts of these frugivores on tree abundance. Tree species more highly dependent on zoochorous seed dispersal will have more room for skewed interaction strengths among their dispersers. In measuring functional redundancy or in trying to predict the role of diversity in species interactions, we must explicitly account for variation in life-history traits

Branching Out: Generating an Evolutionary Tree of Southeast Asian Plants with Computational Tools

Plants in Southeast Asia are historically understudied, and their evolutionary relationships are poorly understood. This lack of an evolutionary history has proven to be an obstacle to further investigation of these species, so this research seeks to create a phylogeny, or evolutionary tree, of these plants using molecular data and computational tools. To accomplish this, I downloaded amino acid and DNA sequences from respected databases. I determined which sequences are best recorded in the species of interest, and utilized a blend of pre-existing tools and scripts written in the Perl programming language to eliminate sequences that could lead to inaccurate results. I fed these “filtered” sequences into programs that create alignments of protein or DNA sequences (MAFFT and Opal). These sequence alignments are used to infer likely relationships among these sequences and, therefore, relationships among the species they were obtained from. The resulting alignments were used to compute the most probable phylogeny, using the inference tool, FastTree. The resulting evolutionary tree will assist in filling a significant gap in our knowledge of the evolutionary history of the plants of Southeast Asia. It will also be directly applicable to the research of our Biology Department’s Dr. Jedediah Brodie, who is investigating how interactions with marsupials and mammals has shaped the evolution of these plant species